Gas turbine engine front architecture

ABSTRACT

A turbine engine is disclosed that includes a fan case surrounding a fan rotatable about an axis. A core is supported relative to the fan case by support structure arranged downstream from the fan. The core includes a core housing having an inlet case arranged to receive airflow from the fan. A compressor case is arranged axially adjacent to the inlet case and surrounds a compressor stage having a rotor blade with a blade trailing edge. The support structure includes a support structure leading edge facing the fan and a support structure trailing edge on a side opposite the support structure leading edge. The support structure trailing edge is arranged axially forward of the blade trailing edge. In one example, a forward attachment extends from the support structure to the inlet case.

CROSS REFERENCE TO RELATED APPLICATIONS

The present disclosure is a continuation of U.S. patent application Ser.No. 11/846,095, filed Aug. 28, 2007.

BACKGROUND

This disclosure relates to a core housing configuration for gas turbineengine that includes a gear driven fan, for example.

Gas turbine engines for commercial aircraft applications typicallyinclude an engine core housed within a core nacelle. In one type ofarrangement known as a turbofan engine, the core drives a large fanupstream from the core that provides airflow into the core. A fan caseand nacelle surround the fan and at least a portion of the core. Acompressor section within the core compresses the air from the fan anddelivers it downstream into a combustion section. One type of compressorsection includes low and high pressure compressors, each with one ormore stages. The compressed air is mixed with fuel and combusted in thecombustion section. The products of this combustion are then delivereddownstream over turbine rotors, which are rotationally driven to providepower to the engine.

The core housing is typically constructed from multiple cases thatsupport various portions of the core. The inlet case is arranged at thefront of the core to receive airflow from the fan. A low pressurecompressor case is arranged behind the inlet case, and an intermediatecase is arranged between the low pressure compressor case and a highpressure compressor case. Typically, the core is supported by the fancase using flow exit guide vanes that straighten the airflow as it exitsa bypass flow path, which is arranged between the fan case and corenacelle. Some turbofan engines include a gear train arranged between thecompressor section and the fan that is used to drive the fan at adesired speed. The gear train is typically supported by the inlet case.The gear train adds significant weight to the front of the core, whichalso must be carried by the flow exit guide vanes.

The flow exit guide vanes typically support the core at an axiallocation aft of the low pressure compressor stages. In one example, theflow exit guide vanes are axially aligned with the intermediate case. Asupport wall extends a significant length from the area of the flow exitguide vanes and intermediate case to the front of the inlet case toprovide adequate support for the gear train. This arrangement isundesirable because it provides limited access to various enginecomponents and makes service and assembly more difficult and costly.Further, the overall axial length of the fan case is larger thandesired, which adds weight and complicates packaging. What is needed isa simplified turbine engine core front architecture that providesdesired support for the gear train while decreasing weight and cost.

SUMMARY

A turbine engine is disclosed that includes a fan case surrounding afan. A core is supported relative to the fan case by support structure,such as flow exit guide vanes, which are arranged downstream from thefan. The core includes a core housing having an inlet case arranged toreceive airflow from the fan. A compressor case is arranged axiallyadjacent to the inlet case and surrounds a compressor stage. In oneexample, the example turbine engine includes a gear train arrangedbetween the fan and a spool. The gear train is axially aligned andsupported by the inlet case. An intermediate case is arranged axiallyadjacent to the compressor case. The support structure is arrangedaxially forward of the intermediate case. In one example, the supportstructure is axially aligned with the compressor case.

These and other features of the disclosure can be best understood fromthe following specification and drawings, the following of which is abrief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a highly schematic cross-sectional view of a gearedturbofan gas turbine engine.

FIG. 2 illustrates a cross-sectional view of a case mounting arrangementillustrating a typical flow exit guide vane configuration relative tothe core housing.

FIG. 3 illustrates a cross-sectional view of an example case mountingarrangement according to the disclosure.

FIG. 4 illustrates an enlarged cross-sectional view of the arrangementshown in FIG. 3 at an intersection between an inlet case and a lowpressure compressor case.

DETAILED DESCRIPTION

A geared turbofan engine 10 is shown in FIG. 1. A pylon 38 secures theengine 10 to an aircraft. The engine 10 includes a core nacelle 12 thatsurrounds a low spool 14 and high spool 24 rotatable about an axis A.The low spool 14 supports a low pressure compressor 16 and low pressureturbine 18. In the example, the low spool 14 drives a fan 20 through agear train 22. The high spool 24 supports a high pressure compressor 26and high pressure turbine 28. A combustor 30 is arranged between thehigh pressure compressor 26 and high pressure turbine 28. Compressed airfrom compressors 16, 26 mixes with fuel from the combustor 30 and isexpanded in turbines 18, 28.

In the example shown, the engine 10 is a high bypass turbofanarrangement. In one example, the bypass ratio is greater than 10, andthe turbofan diameter is substantially larger than the diameter of thelow pressure compressor 16. The low pressure turbine 18 has a pressureratio that is greater than 5:1, in one example. The gear train 22 is anepicycle gear train, for example, a star gear train, providing a gearreduction ratio of greater than 2.5:1. It should be understood, however,that the above parameters are only exemplary of a contemplated gearedturbofan engine. That is, the invention is applicable to other enginesincluding direct drive turbofans.

Airflow enters a fan nacelle 34, which surrounds the core nacelle 12 andfan 20. The fan 20 directs air into the core nacelle 12, which is usedto drive the turbines 18, 28, as is known in the art. Turbine exhaust Eexits the core nacelle 12 once it has been expanded in the turbines 18,28, in a passage provided between the core nacelle 12 and a tail cone32.

Referring to FIG. 2, a core 13 is arranged within the core nacelle 12and is supported within the fan nacelle 34 by structure 36, such as flowexit guide vanes, extending radially inwardly from a fan case 46. Agenerally annular bypass flow path 39 is arranged between the core andfan nacelles 12, 34. The examples illustrated in the Figures depict ahigh bypass flow arrangement in which approximately eighty percent ofthe airflow entering the fan nacelle 34 bypasses the core nacelle 12.The bypass flow B within the bypass flow path 39 exits the fan nacelle34 through a fan nozzle exit area at the aft of the fan nacelle 34.

The core 13 generally includes at least an inlet case 64, a low pressurecompressor case 66, and an intermediate case 76. The inlet case 64guides airflow from the fan 20 to the low pressure compressor case 66.As shown in FIG. 2, the low pressure compressor case 66 in an examplegas turbine engine 80 supports a plurality of compressor stator vanes68. A rotor 70 rotates about the axis A, and, with the compressor statorvanes 68, help compress air moving through the low pressure compressorcase 66.

The guide vanes 36 are axially aligned with the intermediate case 76.The guide vanes 36 secure the intermediate case 76 to the fan case 46.The guide vanes 36 each include at least a rearward attachment 74 and aforward attachment 78, which are arranged on a forward side 89 of theguide vanes 36. The rearward attachment 74 connects to the intermediatecase 76 while the forward attachment 78 connects to the inlet case 64.The rearward attachment 74 extends generally perpendicularly to the axisA. An aft attachment 90 extends from an aft side 91 of the guide vanes36 and intersects with the rearward attachment 74 at the front of theintermediate case 76.

The forward attachment 78 extends a significant distance forward to theinlet case 64, which is generally undesirable. For example, a plumbingconnection area 82 is difficult to access and the axial length of thefan case 46 is longer than desired. The lower pressure compressor case66 is supported through the intermediate case 76 and the inlet case 64in the arrangement shown in FIG. 2.

Returning now to an example of the disclosed arrangement shown in FIG.3, the forward attachment 78 attaches to a front portion of the lowpressure compressor case 66. In this example, the forward attachment 78extends from the guide vanes 36 to support the low pressure compressorcase 66. Together, the forward attachment 78 and guide vanes 36 act as asupport member for the low pressure compressor case 66. The plumbingconnection area 82 is positioned upstream of the forward attachment 78facilitating access to the plumbing connection area 82. In this example,an operator may directly access the plumbing connection area 82 afterremoving the fan stream splitter 86. The plumbing connection area 82typically provides access to a lubrication system 82 a, a compressed airsystem 82 b, or both. The lubrication system 82 a and compressed airsystem 82 b are typically in fluid communication with the gear train 22.

Maintenance and repair of the gear train 22 may require removing thegear train 22 from the engine 10. Positioning the plumbing connectionarea 82 ahead of the forward attachment 78 simplifies maintenance andremoval of the gear train 22 from other portions of the engine 10.Draining oil from the gear train 22 prior to removal may take placethrough the plumbing connection area 82 for example. The plumbingconnection area 82 is typically removed with the gear train 22. Thus,the arrangement may permit removing the gear train 22 on wing orremoving the inlet case 64 from the gas turbine engine 10 separatelyfrom the low pressure compressor case 66. This reduces the amount oftime needed to prepare an engine for continued revenue service, savingan operator both time and money.

Connecting the forward attachment 78 to the low pressure compressor case66 helps maintain the position of the rotor 70 relative to the interiorof the low pressure compressor case 66 during fan rotation. In thisexample, the intermediate case 76 supports a rear portion of the lowpressure compressor case 66 near a compressed air bleed valve 75.

As shown in FIG. 4, a seal 88, such as a “W” seal, may restrict fluidmovement between the inlet case 64 and the low pressure compressor case66. In this example, the seal 88 forms the general boundary between theinlet case 64 and the low pressure compressor case 66, while stillallowing some amount movement between the cases.

The core 13 is provided by a housing having cases secured to one anotherin series to house the compressor and turbine sections and supportvarious components. The inlet case 64 includes an outer diameter wall 96arranged about an inner diameter wall 94. A fixed stator vane 98 extendsradially between and joins the inner and outer diameters walls 94, 96,in the example shown.

The low pressure compressor case 66 is arranged axially adjacent to theinlet case 64. The low pressure compressor case 66 includes an outerdiameter wall 100 that supports variable stator vanes 106 that areactuated by levers 108. In one example, the low pressure compressorsection includes three stages provided by three sets of blades 102supported on the rotor 70.

The intermediate case 76 includes an inner diameter wall 116 arrangedwithin an outer diameter wall 118. The intermediate case 76 is arrangedaxially between the low pressure compressor case 66 and a high pressurecompressor case 120, which is best shown in FIG. 3. The high pressurecompressor case 120 houses the high pressure compressor section.

With continuing reference to FIG. 4, the inlet case 64 includes aforward attachment 78, which extends radially outward and rearward tothe guide vanes 36. The rearward attachment 74 extends radially outwardand forward from the intermediate case 76 to the guide vanes 36. In theexample shown, the forward and rearward attachments 78, 74 are generallyequidistant from the guide vanes 36 to the low pressure compressor case66. The forward and rearward attachments 78, 74 are integral with theinlet and intermediate cases 64, 76 to provide a unitary structure. Theforward and rearward attachments 78, 74 are secured to an end 114 of theguide vanes 36 by a portion 112, which is secured to the end 114. Acavity 110 is provided by the forward and rearward attachments 78, 74and the guide vanes 36, which is arranged outside of the outer diameterwall 100 to enclose the levers 108. In the example shown, the guidevanes 36 are arranged at a generally intermediate axial positionrelative to the low pressure compressor case 66. The forward andrearward attachments 78, 74 are in an overlapping position axiallyrelative to the low pressure compressor case 66, placing the gear train22 in closer proximity to the guide vanes 36.

The gear train 22 is axially aligned with the inlet case 64 in theexample shown. The gear train 22 includes a ring gear 122 andintermediate gears 124, which are constrained relative to the inlet case64. Arranging the guide vanes 36 forward of the intermediate case 76better supports the weight and load distribution attributable to thegear train 22 while providing a more compact fan case 46.

Although an example embodiment has been disclosed, a worker of ordinaryskill in this art would recognize that certain modifications would comewithin the scope of the claims. For that reason, the following claimsshould be studied to determine their true scope and content.

What is claimed is:
 1. A turbine engine comprising: a fan casesurrounding a fan rotatable about an axis; a core supported relative tothe fan case by a support structure and arranged downstream from thefan, the core including a core housing having an inlet case arranged toreceive airflow from the fan, a compressor case axially adjacent to theinlet case and surrounding a compressor stage having a rotor blade witha blade trailing edge, wherein an intermediate case is arranged betweenthe compressor case and a high pressure compressor case; and wherein thesupport structure includes a support structure leading edge facing thefan and a support structure trailing edge on a side opposite the supportstructure leading edge, and the support structure trailing edge arrangedaxially forward of the blade trailing edge, wherein a forward attachmentextends from the support structure to the inlet case, wherein theforward attachment extends radially outward and rearward from the inletcase, wherein the intermediate case supports a rear portion of thecompressor case near a compressed air bleed valve, and comprising arearward attachment extending from the support structure to theintermediate case, wherein the front and rearward attachments aregenerally equidistant from the support structure to their respectiveforward and rearward attachment.
 2. The turbine engine according toclaim 1, comprising variable stator vanes arranged within the compressorcase and including actuating levers connected thereto that are arrangedwithin a cavity provided by the front and rearward attachments.
 3. Theturbine engine according to claim 2, wherein the front and rearwardattachments are generally equidistant from the support structure totheir respective forward and rearward attachment in the axial direction.